Fluid supply distributor

ABSTRACT

A fluid supply distributor communicates fluid from a stationary fluid source to a rotating hydraulic motor. The distributor includes a housing with main ports for connection to high and low pressure at the source. A shaft rotating in the housing is attached to the motor and includes motor ports for connection to the rotating motor. A sleeve in the housing surrounds the shaft, and the sleeve and shaft define interfacing sealing surfaces. The housing, the sleeve, and the shaft include passages for communicating fluid between the main ports and the motor ports. The sleeve is normally retained in a stationary position, but is released to rotate within the housing should the shaft seize within the housing. The passages include spaced supply grooves at the sealing surfaces connected to the main ports and thus maintained at different pressures. Bearing assemblies adjacent the sealing surfaces mount the shaft for rotation and are lubricated in a balanced fashion by leakage of fluid between the sealing surfaces from both supply grooves.

This is a divisional application of application Ser. No. 695,595, filedJune 14, 1976, now U.S. Pat. No. 4,040,338.

The present invention relates to a new and improved fluid supplydistributor for supplying pressurized fluid from a source to a rotatinghydraulic motor of the type employed with an industrial machine tool.

Large industrial machine tools such as lathes typically employ arotating hydraulic motor to actuate a rotating workpiece holder such asa chuck or a collet. Normally the rotating motor is operated bypressurized hydraulic fluid from a stationary source. It is necessary toprovide an interconnection between the stationary source and therotating motor. Typically, a fluid supply distributor is used to performthis function. For example, one typical fluid supply distributor isdisclosed in U.S. Pat. No. 3,417,672.

Fluid supply distributors of the type used in the past include an outerstationary housing having ports for connection to a fluid pressuresource. A stem or shaft is mounted for rotation within the housing ofthe distributor, and the stem or shaft typically either comprises a partof or is connected to the rotating cylinder of the hydraulic motor. Thepiston of the motor rotates with and reciprocates in the cylinder andoperates the workpiece holder.

The mounting of the shaft for rotation within the housing providesproblems in fluid supply distributors used in the past. In onearrangement, the housing and shaft are provided with surfaces formingjournal bearings lubricated by leakage fluid. In another arrangement,bearing assemblies may be provided. In either case, it may happen thatthe bearing assemblies or bearing surfaces malfunction due tooverheating, inadquate lubrication, or the like, with the result thatthe shaft is seized within the housing. Since the rotary motor and theshaft or stem are continuously rotated by the machine tool, seizure ofthe shaft can result in rotation of the housing of the fluid supplydistributor, and of fluid supply hoses and other equipment connectedthereto. Consequently, seizure can lead not only to destruction of thedistributor but to a dangerous condition.

Among the important objects of the present invention are to provide anew and improved fluid supply distributor; to provide a distributorwherein the rotation of the stationary housing upon seizure of therotating shaft is prevented; to provide a distributor whereindestruction of the entire unit does not result from seizure of therotating shaft; to provide a fluid supply distributor having an improvedbearing lubrication system; to provide a fluid supply distributorcapable of withstanding high speed and heavy loads; and to provideimprovements in the structural features, the cost, and the safety offluid supply distributors.

Briefly, in accordance with the above and other objects of the presentinvention, there is provided a fluid supply distributor forcommunicating fluids at high and low pressures between a stationaryfluid source and a rotating hydraulic motor. The distributor includes astationary housing with main ports for connection to the source,together with a rotating shaft mounted in the housing and having motorports for connection to the rotating hydraulic motor. A sleeve isinterposed between the housing and the shaft, and interfacing sealingsurfaces are defined on the interior surface of the sleeve and theexterior surface of the shaft. Passages within the distributorintercommunicate the main ports and the motor ports. In accordance withan important feature of the invention, the sleeve is normally maintainedin a stationary position within the housing; however, upon seizure ofthe shaft, the sleeve is able to break away from the housing and rotatewith the shaft while the housing remains stationary.

Fluid is intercommunicated from stationary passages in the housingassembly to passages in the rotating shaft by means including a pair ofcircular grooves defined in one of the sealing surfaces. A pair ofbearing assemblies adjacent the bearing surfaces support the shaft forrotation and are lubricated by leakage flow along thhe sealing surfacesfrom the grooves. In accordance with an important feature of theinvention, each bearing assembly is not only lubricated by direct flowfrom an adjacent, first groove, but also by leakage flow from thenon-adjacent groove supplied by leakage collection groove and alubricating passage. In this manner, both bearing assemblies areprovided with equalized lubrication flow regardless of thepressurization conditions of the supply grooves.

The above and other objects and advantages and novel features of thepresent invention will become apparent from the following detaileddescription of a preferred embodiment of the invention illustrated inthe accompanying drawings, wherein:

FIG. 1 is a simplified diagrammatic illustration of portions of amachine tool, a rotating hydraulic motor, and a fluid supply distributorconstructed in accordance with the present invention;

FIG. 2 is a sectional view on an enlarged scale of the fluid supplydistributor taken along the line 2--2 of FIG. 1, but illustrating thedistributor in detail rather than in simplified form;

FIG. 3 is an end, elevational view of the distributor taken from theline 3--3 of FIG. 2;

FIG. 4 is a fragmentary, sectional view on an enlarged scale taken alongthe line 4--4 of FIG. 3; and

FIG. 5 is a fragmentary, sectional view on an enlarged scale taken alongthe line 5--5 of FIG. 3.

Having reference now to the accompanying drawings, in FIG. 1 there isillustrated in simplified and diagrammatic form a fluid supplydistributor generally designated as 10 associated with a rotatinghydraulic motor 12 and a machine tool 14 indicated in broken lines. Themachine tool 14 includes a conventional collet or chuck workpiece holder(not shown) operated by reciprocation of an actuating tube 16 mountedconcentrically within a rotating spindle 18 of the tool. The rotatinghydraulic motor 12 functions to move the rotating actuating tube 16 inopposite directions along its axis, while the fluid supply distributor10 communicates fluid between a stationary fluid source and the rotatingmotor 12.

As indicated in simplified form in FIG. 1, the rotating hydraulic motor12 includes a rotating cylinder 20 typically attached for rotation withthe spindle 18 and enclosing a rotating piston assembly 21 attached tothe tube 16. A pair of passages 22 and 24 formed in the cylinder 20permit selective pressurization of opposite sides of the piston assembly21 in order to reciprocate the piston assembly 21 and the tube 16thereby to operate the workpiece holder.

The fluid supply distributor 10 includes a stationary housing assemblygenerally designated as 25 including a pair of main or supply ports 26and 28 adapted to be connected by suitable conduits and valves with highpressure and low pressure fluids supplied from a stationary source.Rotatably mounted within the housing assembly 25 is a shaft or stem 30attached to the rotating cylinder 20. Passages 32 and 34 in shaft 30communicate with passages 22 and 24 in the cylinder. The illustratedarrangement is of the so-called "through hole" type and the shaft 30,the piston assembly 21 and the tube 16 are hollow to permit a workpiecesuch as bar stock or the like to be fed therethrough.

With reference now to FIGS. 2-5, the fluid supply distributor 10 of thepresent invention is illustrated in more detail. The housing assembly 25includes a stationary housing including a body member 36 to which arefastened a pair of end covers 38 and 40. In accordance with an importantfeature of the invention, the housing assembly 25 further includes asleeve or intermediate shaft 42 within which the shaft 30 is received. Apair of bearing assemblies 98 and 100 mounted between the shaft 30 andthe sleeve 42 support the shaft 30 for rotation within the housingassembly 25. In the event of a seizure of the shaft 30 to the sleeve 42,the sleeve 42 is able to break away from the stationary housing androtate without destroying the stationary housing or creating a dangerouscondition.

More specifically, the assembled body 36 and end covers 38 and 40 definea generally annular internal recess within which the cylindrical sleeve42 is received. The interior surface of sleeve 42 defines a generallycylindrical sealing surface 44 interfacing with a sealing surface 46defined upon the exterior of the shaft 30. Sealing surfaces 44 and 46are spaced apart slightly from one another so that they do not contactone another and so that a restricted path between the surfaces forcontrolled leakage of fluid for lubrication is provided.

At axially spaced locations along the interfacing sealing surfaces 44and 46 there are disposed a pair of rotary fluid interconnections 48 and50. In the illustrated arrangement, the interconnection 48 includes acircular supply groove 52 formed in surface 44 and an aligned port 54formed in surface 46. Similarly, the rotary fluid interconnection 50includes a supply groove 56 and a port 58.

In order to communicate fluid from the main or supply ports 26 and 28 tothe rotary fluid interconnections 48 and 50, the body 36 includes a pairof passages 60 each extending radially inward from one of the supplyports. A pair of passages 62 normally aligned with passages 60 extendradially inwardly through the sleeve 42 to the grooves 52 and 56. Only asingle passage 60 and passage 62 are illustrated in the drawings, andappear in FIGS. 2 and 4.

Fluid supplied through the supply passages 60 and 62 to the grooves 52and 56 communicates with the passages 32 and 34 respectively by means ofthe ports 54 and 58. As illustrated in FIG. 1, the passages 32 and 34communicate with passages 22 and 24 in the rotating hydraulic cylinder20 of motor 12. In the illustrated arrangement, the grooves 52 and 56also communicate with additional ports 64 and 66 and additional passages68 and 70 formed in shaft 30. Fluid from these additional passages 68and 70 may be supplied to control the operation of check valvesassociated with the rotating hydraulic motor 12 in conventional manner.

As indicated above, in accordance with one feature of the invention thesleeve 42 is releasably retained in a stationary position. Havingreference now to FIG. 4, there is illustrated one arrangement forreleasably retaining the sleeve 42 fixed to the housing 25. A fitting 72is threaded into each of the main or supply ports 26 and 28. A sealingand coupling bushing or element 74 is captured in each of the passages60 by the fittings 72. The bushing is provided with a pair of seals 76and 78 at opposite ends of a central axial opening 80. Consequently,fluid passes through the opening 80 between the passages 60 and 62,while the seals 76 and 78 prevent the admission of fluid to the regionbetween the body 36 and the sleeve 42.

As can be seen with reference to FIG. 4, the innermost end portion ofthe bushing 74 is received in an enlarged portion or recess 82 in theouter surface of the sleeve 42. Engagement of the bushing in the recess82 serves releasably to retain the sleeve 42 in position. The bushingmay be fabricated of any frangible material such as a suitable metal orplastic so that when subjected to a predetermined stress, the bushingwill fracture or shear, thereby permitting rotation of the sleeve 42within the housing.

In FIG. 5 there is illustrated an indicating arrangement generallydesignated as 84 for providing an indication of movement of the sleeve42, and also, if desired, for providing or augmenting the releasableretention of the sleeve 42 within the housing. A recess 86 is formed inthe outer surface of the sleeve 42, and a detention device indicated asa ball 88 held by a retainer 90 is biased into the recess 86 by means ofa spring 92 captured beneath an adjustable cap 94. The ball 88 tends toretain the sleeve 42 in a stationary position, and the degree of theretention force is determined by the configuration of the recess 86 andby the force applied to the ball by the spring 92.

When the retention force is overcome and the sleeve 42 rotates withinthe housing, the ball is lifted by camming action of the base of therecess 86. An indicator element 96 is lifted in response to outwardmovement of the ball to project from the cap 94 and provide a readilyvisible indication to the operator of movement of the sleeve 42.

In order to permit high speed operation of the rotating hydraulic motor12 and to permit operation under heavy loads, the sealing surfaces 44and 46 do not contact one another, but rather are accurately machined toprovide for restricted and controlled leakage flow of pressurized fluidfrom the grooves 52 and 56 for lubrication purposes. For example, in theillustrated embodiment the surfaces are spaced apart in the radialdirection by a distance in the range of 0.0014 inch minimum and 0.0018inch maximum. The circular bearing assemblies 98 and 100 are sandwichedbetween the shaft 30 and the sleeve 42 adjacent the opposite ends of thesealing surfaces 44 and 46 in order to position the shaft 30 and tosupport the shaft for rotation.

In accordance with an important feature of the invention, there isprovided an arrangement for lubrication of the bearing assemblies 98 and100 in a balanced fashion regardless of pressure differences existingbetween the grooves 52 and 56. Each assembly is lubricated by directleakage flow from the adjacent groove 52 and 56. Thus, assembly 98 islubricated by flow from groove 52 across a segment 44A of the sealingsurface 44. Similarly, assembly 100 is lubricated by leakage flow acrossa segment 44B of the sealing surface 44.

During normal operation of the fluid supply distributor 10, one of thesupply ports 26 and 28 is supplied with fluid at a relatively highpressure while the other port acts as a return for fluid at a relativelylow pressure. Consequently, one of the grooves 52 and 56 contains fluidat a substantially higher pressure than the other and direct leakagelubrication across sealing surface segments 44A and 44B is unbalanced inthat the assembly adjacent the higher pressure groove receives a largerflow of lubricating fluid than the assembly adjacent the lower pressuregroove.

In order to provide balanced lubrication, each bearing assembly 98 and100 is also lubricated by means of leakage flow from the nonadjacentgroove. More specifically, a pair of leakage collection grooves 101 and102 are defined in the sleeve 42 between the supply grooves 52 and 56.Fluid flows from groove 52 over a sealing surface segment 44C to thegroove 101 and fluid flows over sealing surface segment 44D from thegroove 56 to the groove 102. Slingers are provided in the inner surface46 for facilitating the collection of leakage fluids within the grooves101 and 102.

Fluids collected within the grooves 101 and 102 are communicated to thebearing assemblies 98 and 100 by a pair of passages 104 and 106.Specifically, passage 104 extends through the sleeve 42 from the groove101 to the bearing assembly 100, while passage 106 extends from thegroove 102 to the bearing assembly 98.

Preferably, in order to provide balanced lubrication, the sealingsurface segments 44A, 44B, 44C and 44D are all of approximately the samelength. Thus, for any given pressure conditions, fluid flowing acrosssegments 44A and 44C from groove 52 in opposite directions to theassembly 98 and groove 101 respectively will be approximately equal inamount. Similarly with respect to the groove 56, approximately equalflows occur across the segments 44B and 44D to the assembly 100 and thegroove 102. Since assemblies 98 and 100 both receive leakage flows fromboth grooves 52 and 56, the quantity of lubricating fluid supplied toboth bearing assemblies is essentially equal.

Under some conditions it may be desirable to provide externallubrication of the bearing assemblies 98 and 100. For this purpose, thepassages 104 and 106 are communicated with passages 108 and 110extending radially outward through the sleeve 42. These passages 108 and110 are accessible through an opening 112 in the body 36. As illustratedin FIG. 2 this opening is normally closed by a plug member 114.

During operation of the fluid supply distributor 10, the sealingsurfaces 44 and 46 and the bearing assemblies 98 and 100 arecontinuously lubricated by controlled leakage fluid flow. The body 36 isprovided with a sump or cavity 116 for collecting fluid flowing throughthe bearing assemblies 98 and 100. Although not illustrated in thedrawings, the sump 116 is provided with an outlet for discharge offluid.

In order to channel fluid from the assemblies 98 and 100 to the sump 36,the outer side of each bearing assembly communicates with a circularfluid collection passage or chamber 118. One of the passages 118 isdefined by end cap 38 in combination with a bearing retainer 120attached to and rotatable with the shaft 30. The other passage 118 isdefined within the end cap 40. As illustrated in FIG. 2, the lowermostportions of the passages 118 open into the sump 116.

It is desirable to prevent the leakage of fluid from the passages 118outwardly in the axial direction between the end cap 38 and bearingretainer 120, and the end cap 40, and the shaft 30. Advantageously, thisis accomplished without the use of resilient seal members or the likewhich would not only add expense but also would create a frictionalloading of the rotation of shaft 30. In accordance with the invention,this sealing is provided by the use of secondary sealing regions 122 and124 defined between the end caps 38 and 40 and the retainer 120 and theshaft 30 respectively. The tolerances of these regions 122 and 124 areselected so that free rotation is attained and so that only limitedfluid flow takes place across these regions. If desired, the surfaces ofregions 122 and 124 may be machined with grooves (not shown) to providea labyrinth seal.

Secondary leakage flow travelling across sealing regions 122 and 124 iscollected in secondary leakage collection chambers or passages 126defined in the end caps 38 and 40 axially outwardly of the maincollection passages 118. The lowermost sections of these passages alsocommunicate with the sump 116. The end caps include wall portions 128and 130 separating the lowermost portions of the collection passages 118and 126 (FIG. 2). These walls act as shields to prevent the splashing offluids thrown directly from the bearing assemblies 98 and 100 into thesecondary collection passsages 126 so that these fluids do not escapefrom the end caps 38 and 40.

In operation of the fluid supply distributor 10, assume that supply port26 is interconnected with a source of fluid at a relatively highpressure and that supply port 28 is interconnected with a region of lowpressure. Pressurized fluid enters the port 26 and flows to groove 52through passages 60 and 62 by way of bushing 74 (FIG. 4). Groove 52 ispressurized throughout its circular extent and as a result passages 34and 68 in the rotating shaft 30 are pressurized. Consequently, passage24 (FIG. 1) in the rotating cylinder 20 is pressurized in order to biasthe piston assembly 21 in the direction to extend the actuating tube 16.

Low pressure fluid is returned from the opposite side of piston assembly21 through the passage 22 to passage 32 in rotating shaft 30. This lowpressure fluid is directed through port 58 into groove 56 from which itflows via passages 60 and 62 to port 28.

Pressurized fluid in restricted and controlled quantities flows fromgroove 52 in opposite directions across leakage paths underlying sealingsurface portions 44A and 44C. The flow across portion 44A directlylubricates bearing assembly 98. The flow across portion 44C enterscollection groove 101 and flows through passage 104 to lubricate bearingassembly 100. Consequently, both bearing assemblies 98 and 100 areprovided with equalized lubrication flows. Fluid flowing through thebearing assemblies 98 and 100 is collected in passages 118 and 126 fromwhich it flows to the sump 116.

Under some conditions it may occur that the sealing surfaces 44 and 46,or perhaps the bearing assemblies 98 and 100, exhibit abnormally highfriction and cause shaft 30 to become seized. For example, thelubrication of the surfaces and bearing assemblies may be insufficientdue to a failure of the source of high pressure fluid, or a fragment ofa worn bearing or contaminants in the fluid may become lodged betweenthe sealing surfaces 44 and 46. Under these circumstances, the shaft 30,which is rotated by the spindle 18, applies a substantial rotationaltorque to the sleeve 42. The sleeve 42 is capable of breaking away fromthe housing assembly 25 due to deflection of the ball 88 and/or due tofracture or shearing of the bushing 74. When this occurs, the sleeve 42rotates together with the shaft 30. The remainder of the housing is notdamaged, and a dangerous abrupt rotation of the housing is prevented.

When sleeve 42 rotates, the indicator elements 98 are extended so thatthe operator of the machine is immediately apprised of the malfunction.Once the machine is shut down, it is a relatively simple and inexpensivematter to disassemble the fluid supply distributor 10 and reassemble itin proper working order after correcting the cause of the malfunction.

While the invention has been described with reference to details of theillustrated embodiment, it should be understood that such details do notlimit the scope of the invention as defined in the following claims.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. In a fluid supply distributor for a rotatinghydraulic motor, the combination comprising:a stationary housingassembly; a shaft mounted for rotation in said housing assembly;interfacing generally cylindrical sealing surfaces formed on saidhousing assembly and shaft; said sealing surfaces being spaced apart todefine restricted leakage flow regions therebetween; a pair of circularfluid supply grooves in one sealing surface; a pair of circular bearingassemblies interposed between said housing assembly and shaft adjacentsaid sealing surfaces and flanking said supply grooves; a pair ofcircular leakage fluid collection grooves in one sealing surface andflanked by said supply grooves; two supply passages in said housingassembly and communicating with said supply grooves for pressurizingsaid grooves at different pressures; two motor passages in said shaftand communicating with said supply grooves for applying said differentpressures to the rotating hydraulic motor; a first of said supplygrooves being located along said sealing surfaces between a first ofsaid bearing assemblies and a first of said leakage grooves, and thesecond supply groove being located along said sealing surfaces betweenthe second bearing assembly and the second leakage groove; each bearingassembly being lubricated by direct leakage flow from the adjacentsupply groove; and a pair of lubrication passages interconnecting thefirst leakage groove to the second bearing assembly and the secondleakage groove to the first bearing assembly for lubrication of eachbearing assembly by leakage flow from the nonadjacent supply groove,said housing assembly further including a sleeve surrounding said shaftand defining one sealing surface; and means for releasably retainingsaid sleeve in a stationary position in said housing assembly and forpermitting rotation of said sleeve within said housing assembly inresponse to seizure of said sealing surfaces.
 2. The combination ofclaim 1, the leakage paths along said sealing surfaces between saidsupply grooves and said bearing assemblies and said leakage grooves allbeing approximately of the same length.
 3. The combination of claim 1,further comprising a sump in said housing assembly, and collectionpassages for channeling fluid from said bearing assemblies to said sump.